DESCRIPTION: This K01 Mentored Research Scientist Development Award will provide the candidate, Alia Al-Tayyib, PhD with advanced training and structured mentoring to facilitate her transition to research independence. The candidate's goal is to become an independent investigator with expertise in network approaches to understand risk related to HIV and hepatitis C virus with an emphasis on transition to injection drug use among youth. The proposed scope of work will fill a marked gap in the existing literature by examining an emerging pattern of drug use, from a social networks perspective. The nonmedical use of prescription drugs is the fastest growing drug problem in the United States, resulting in more deaths per year than heroin and cocaine combined. Opioid pain relievers are the most commonly misused prescription drug and young people misuse them at alarming rates. Furthermore, the population prevalence of injection drug use among youth is on the rise. This emerging drug abuse pattern, i.e., the transition from misuse of prescription opioid pain relievers to injection heroin use, is largely under-studied. Understanding the factors that accelerate or inhibit transition from oral ingestion of prescription opioids to injection drug use among young people is critical given the risk injection drug use poses for acquiring HIV and/or HCV. Social networks influence pathways into drug injecting and youth are particularly vulnerable to the influence of their social networks. The candidate will use a two-step approach to examine factors that influence the transition from prescription opioid misuse to injection drug use. Observations of standardized lifetime timeline assessments with youth in substance treatment programs will be followed by the recruitment of 120 participants between 15 and 24 years who currently misuse prescription opioids or have transitioned to injection. Participants will be recruited using respondent driven sampling (RDS) and will be guided through an in-depth tracing of their social network. The project is divided into three sequential stages, where each training goal is matched with a research aim in which the investigator will apply her new skills. The candidate will pursue training in (1) substance use and co-occurring mental health issues among youth and young adults, (2) social network methodology and analysis, and (3) longitudinal analysis. The following specific aims guide the three stages. Aim 1: elucidate the complex risk environment and co-occurring disorders associated with transition to injection, Aim 2: examine the structural attributes of, and exposure to risk within, the social networks of youth who misuse prescription opioids or have transitioned to injection, and Aim 3: determine the feasibility of RDS augmented with social network tracing for longitudinal study. The K01 award will provide the candidate with protected time to develop the expertise, pilot data, and publication record necessary to establish research independence and position her as one of a handful of doctoral-trained epidemiologists with social network expertise. Furthermore, the K01 will situate the candidate to study future emerging patterns of drug use and their relationships to injection initiation and to other risks.